Spinal implants for aligning the spine and maintaining desired spacing of the vertebrae for spinal fusion procedures are well known. Such spinal implants typically comprise a pair of stainless steel rods which extend longitudinally along that portion of the spine to be fused and which attach to the vertebrae via clamps. The clamps are typically attached to the rods via set screws which engage each rod at a desired point along the length thereof as the rod passes through an aperture formed within the clamp. Thus, by tightening the set screw, the rod is held in place relative to the clamp. Threaded fasteners, i.e., self tapping screws, extend through the clamps and engage the lateral mass of the sacrum and/or the transverse processes of desired vertebrae. Thus, a plurality of such clamps attach each rod to the spine.
However, in order to accommodate the specific anatomical structure of a particular patient's spine, the rods must commonly be modified, i.e., bent. As those skilled in the art will appreciate, each individual patient's spine is structurally unique, i.e., having unique curvature and having a lateral masses and transverse processes of different sizes, shapes, and locations, thereby necessitating such bending of the rods utilized according to the prior art. Thus, the method for attaching such contemporary spinal implants comprises repeatedly positioning the rods along the spine to determine the amount of bending necessary, and then bending the rods so as to cause them to conform to the configuration required by that particular patient's specific anatomical configuration. Thus, it commonly requires several attempts, i.e., trial placements and bending of the rods, in order to achieve adequately configured, i.e., bent, rods which conform to a particular patient's anatomy.
Not only is such modification or bending of the rods inconvenient and time consuming, but it also increases the risks to the patient associated with the surgical procedure. Increasing the length of time during which the spine must be exposed in order to facilitate such modification of the rods inherently increases the risk of infection. Additionally, a greater amount of anesthetic is required in order to maintain the patient in the required anesthetized condition for such a prolonged period of time. As those skilled in the art are aware, substantially increased risk is associated with increased anesthetic.
Further, each attach point, i.e., the point where each rod is attached to a vertebra via a clamp, comprises two different threaded fasteners, the loosening of either of which results in undesirable loss of support at that attach point. Thus, if either the set screw which attaches the clamp to the rod or the screw which attaches the clamp to a vertebra loosens after completion of the surgical implant procedure, then the vertebra associated therewith does not receive sufficient support for rigid fixation or tissue stabilization, and thus injury to the patient may occur and/or additional surgery may be required.
As those skilled in the art will appreciate, all of the various components associated with such implants, i.e., the rods, clamps, set screws, and screws, must be comprised of a bio-compatible material. To date, only stainless steel and titanium have been found to possess both the required structural strength and adequate bio-compatibility. However, even these materials may degrade upon prolonged exposure to biological environments. Further, metal components are difficult to modify, i.e., bend and inhibit post-operative imaging.
As such, although the prior art has recognized to a limited extend the problem of providing a spinal implant for tissue stabilization of a portion of the spine, the proposed solutions have, to date, only achieved limited success in providing a satisfactory remedy.
Thus, it would be beneficial to provide a spinal implant comprised of a material having greater bio-compatibility than stainless steel or titanium and which is suitable for long-term use and which also does not require modification during the surgical implant procedure and allows enhanced post-operative imaging capability. It would further be beneficial to provide a spinal implant which utilizes standardized components in order to eliminate the requirement for routine modification during the surgical procedure.